In the oilfield services industry, and other industries such as construction, mining, farming, and logging, it is common to have to support or transport heavy equipment, such as wheeled machinery, on unpaved soft ground, such as mud, swamp, wetlands, tundra, muskeg and the like. Heavy equipment may sink into such soft ground and become stuck. To avoid this problem, ground cover mats may be used to construct a temporary platform or roadway for the machinery.
The prior art includes examples of reinforced rubber ground cover mats. Canadian Patent 2,473,000 (Fowler et al.) discloses a rubber access mat that includes a rubber slab and a rigidifying grid of reinforcing wire embedded within the rubber slab. The grid consists of a plurality of parallel spaced wires extending between opposed side edges of the slab for most of the width of the rubber slab and a plurality of parallel spaced wires extending between the opposed end edges for most of the length of the rubber slab. Use of reinforcing wire having sizes between ten gauge and three gauge is disclosed. In certain applications, however, the wire grid may tend to cut through the rubber when heavy loads are applied, and thereby form voids that can damage the mat and make it susceptible to moisture infiltration.
Canadian Patent 2,647,547 (Lukasik et al.) and U.S. Pat. No. 7,404,690 (Lukasik et al.) disclose a ground cover mat formed of a one-piece cage that includes two vertically separated layers of orthogonally arranged rebars, which are welded together. The layers are connected by vertically extending connecting rebars that are welded to the rebars of the layers at the intersections to produce a monolithic one-piece cage. The one-piece cage is encased in a flexible material formed of crumb rubber, urethane, and fibers from vehicle tires. However, the cage may require a large amount of rebar to give the mat a desired rigidity, which can make the cage both heavy and labor intensive to manufacture.
Canadian Patent 2,697,174 (Lukasik) and U.S. Pat. No. 7,427,172 (Lukasik) disclose a ground cover mat formed from a plurality of wood planks that are embedded and encased in rubber. In certain applications, however, the wood planks may break or otherwise be damaged if the mat is subjected to heavy loads that are localized over the wood planks.
Therefore, a need continues to exist for improved rubber ground cover mats and methods for manufacturing rubber ground cover mats.